Construction equipment utilize a power source such as a diesel engine to provide power to move the construction equipment from location to location and to power the systems thereon. One of the systems generally associated with a piece of construction equipment is a hydraulic system that supplies hydraulic fluid under pressure, as directed by an operator, to various operational components on the equipment. The hydraulic system includes a hydraulic pump that is driven by the engine. The pump reflects a load onto the engine based upon the demand of the hydraulic fluid during operation of the equipment. If the engine is operating at a very low rpm the available pressure and volume from the pump may be diminished. To increase the pressure and/or volume the engine rpm is increased to provide more available power to the hydraulic system. Most hydraulic systems involve fluid drawn from a reservoir by a pump and is forced through a shifted valve into an expandable chamber of a cylinder, which communicates with the work piece, ultimately performing useful work. The hydraulic fluid is typically returned from the work cylinder to the reservoir when the cylinder is retracted.
The engine of the construction equipment includes a throttle that is under the control of the operator either directly or indirectly. A direct linkage of the throttle to an operator control allows the operator to mechanically reposition the throttle to alter the speed of the engine. The speed of the engine is subject to the load placed thereon either directed mechanically or by way of the hydraulic and/or electrical systems. In the case of an indirect control the engine system may be under the control of an engine control system that reads the operator input, interprets the input and actuates the throttle and/or other elements of the engine to thereby alter performance of the engine based upon needs of the construction equipment as directed by the operator. The engine control system is responsive to the needs of the various loads placed upon the engine and may even include a priority in which certain elements may receive power to the determent of others in the event that the engine is incapable of providing sufficient power to meet all needs. This is known as load shedding where the engine control system sheds some of the load when it anticipates an insufficient output from the engine to meet the load requirements. The engine control system depends upon a prediction of the engine load and such prediction methods can result in incorrect actions when certain transient scenarios occur, such as when the difference between the command engine speed and actual engine speed are large due to a difference in the response characteristics of the throttle and the engine. A problem often encountered is that systems may be inappropriately shed to unload the engine when a transient scenario occurs.
What is needed in the art is an improved engine control system that can compensate for transient scenarios.